It is necessary in many situations to precisely detect the amperage in an at least periodically current-carrying conductor. This is done, for example, in automotive engineering to determine electrical parameters of generators and electrical drives while these units are in operation. A contactless, low-loss and potential-free measurement of the electrical current is needed for this purpose.
According to the related art, shunt resistors are currently used to measure currents. Their high power loss and additional self-inductance are undesirable, especially at high amperages. In addition, they do not ensure electrical isolation between the measuring circuit and the main circuit.
Magnetic field sensors, e.g., Hall sensors, lateral magnetotransistors, magnetoresistive resistors, etc., which are able to precisely measure the magnetic field effect of a current-carrying conductor, are also known. The advantage of these sensors lies, in particular, in the electrical isolation between the measuring circuit and the main circuit, the low or even completely non-existent power loss, and the absence of quantities influencing the current to be measured, for example inductive feedback or resistance.
However, a problem with the use of magnetic field sensors to measure current is that interference, i.e., stray, fields of additional current conductors located adjacent to the conductor to be measured exist or are generated by rotating magnetic fields in the vicinity of generators. This makes it difficult to discriminate between the magnetic field to be measured by the magnetic field sensor and parasitic stray fields in the surrounding area.
One known method of avoiding such difficulties is to shield the magnetic field sensor against interfering magnetic fields and to concentrate the magnetic field to be measured, using a magnetic circuit. However, shielding for highly sensitive sensors is very complex and expensive. Magnetic circuits are also expensive and, in addition, not only take up a great deal of mounting space but are difficult to assemble. A further disadvantage of magnetic circuits is the fact that they have a tendency to become saturated and thus introduce a certain non-linearity between the amperage and magnetic field strength into the measurement.